An international team of astronomers discovered emission from clouds of cold cosmic dust surrounding the Earth-sized temperate world Proxima b, discovered in 2016 and the closest planet to the Solar System, and believed there may be more hidden planets yet to find.
"The dust around Proxima is important because, following the discovery of the terrestrial planet Proxima b, it's the first indication of the presence of an elaborate planetary system, and not just a single planet, around the star closest to our Sun," Guillem Anglada, the lead author of the new study, was quoted as saying in a news release.
Dust belts are the remains of material that did not form into larger bodies such as planets. The particles of rock and ice in these belts vary in size from the tiniest dust grain, smaller than a millimetre across, up to asteroid-like bodies many kilometres in diameter.
Proxima Centauri, the closest star to the Sun, is a faint red dwarf lying just four light-years away in the southern constellation of Centaurus (The Centaur).
According to the new Atacama Large Millimeter Array (ALMA) observations, detailed in a study to appear in Astrophysical Journal Letters, dust appears to lie in a belt that extends a few hundred million kilometres from Proxima Centauri and has a total mass of about one hundredth of the Earth's mass. This belt is estimated to have a temperature of about -230 degrees Celsius, as cold as that of the Kuiper Belt in the outer Solar System.
There are also hints in the ALMA data of another belt of even colder dust about ten times further out. If confirmed, the nature of an outer belt is intriguing, given its very cold environment far from a star that is cooler and fainter than the Sun. Both belts are much further from Proxima Centauri than the planet Proxima b, which orbits at just four million kilometres from its parent star.
Co-author Pedro Amado from the Instituto de Astrofísica de Andalucía (CSIC), Granada, Spain, explains that this observation is just the start.
"These first results show that ALMA can detect dust structures orbiting around Proxima. Further observations will give us a more detailed picture of Proxima's planetary system. In combination with the study of protoplanetary discs around young stars, many of the details of the processes that led to the formation of the Earth and the Solar System about 4600 million years ago will be unveiled. What we are seeing now is just the appetiser compared to what is coming!" Amado explains the implications of the discovery.
